The invention relates to a pressure-release device for a transmission housing through which a transmission shaft extends
In order to avoid churn losses, it is known to pressurize the interior of a engine-driven transmission. The fluid which collects in a low-lying collection area of the transmission housing is returned to a storage container by the overpressure via a communication conduit located in the bottom area of the transmission housing. Except for the communication conduit, the transmission housing is sealed, especially where shafts enter into the housing. As a result of the overpressure in the transmission housing, a higher fluid level tends to develop in the storage container during operation than during standstill when no overpressure prevails. However, the overpressure drops only very slowly after a drive engine is shut off, so that considerable time elapses until a fluid exchange takes place via the communication conduit and a stationary fluid level is adjusted in the transmission housing and in the storage container. This time delay can result in erroneous estimations when checking the fluid level.
An object of the present invention is to provide a means for releasing an over-pressure in a transmission housing.
This and other objects are achieved by the present invention wherein a venting or pressure release system releases pressure from a transmission housing through which extends a transmission shaft. A lower part of the transmission housing forms a collector in which fluid collects. A conduit communicates the collector with a storage container which is substantially sealed against the transmission housing. An overpressure in the transmission housing forces fluid from the collector through the conduit into the storage container. A pressure-release conduit communicates the transmission housing above the collector to the storage container. A shutoff device closes the pressure-release conduit when the transmission shaft is rotating and opens the pressure-release conduit when the transmission shaft is not rotating. This makes possible a rapid compensation of fluid after the transmission has been turned off so that the fluid level can be reliably determined. The shutoff device may be a pilot-controlled valve or a fluid barrier.